Historically, at the Idaho National Engineering Laboratory (INEL), specifically, the Idaho Chemical Processing Plant (ICPP), aluminum-clad nuclear fuels have been dissolved in dilute (4 to 7 M) nitric acid (HNO.sub.3) containing 0.001 to 0.01M mercury. Some mercury, as mercuric nitrate Hg(NO.sub.3).sub.2, is reduced on the surface of the aluminum alloy, forming a Hg-A1 amalgam that enables rapid dissolution of the protective oxide film and metal substrate in nitric acid. The net reaction for a system in which nitrogen oxides are recovered and recycled is, as in Equation (1), approximately: ##EQU1## Mercury catalyzed aluminum fuel dissolution is rapid, efficient, and highly exothermic. Fuel dissolution rates are limited primarily by the ability to remove excess heat and to control foam. Unfortunately, however, mercury is an EPA listed Resource Conservation Recovery Act (RCRA) hazardous waste and its presence in the resulting high-level waste is sufficient to render it into "mixed hazardous waste".
Some development work has been done to explore the feasibility of an electronic aluminum dissolution flowsheet, i.e., to use a flow of electrons through the nitric acid dissolvent via an induced current with a voltage exceeding the ionization potential of the fuel components to enhance dissolution. Although this concept appears to be feasible, its development and the installation and operation of a new facility would be expensive. Hence, the desirability of a flowsheet (process flow) chemically similar to the one historically used at ICPP and using existing ICPP facilities, but with a non-toxic substitute for mercury, is obvious.